Name and / or address. It seems you can't do it at the post office any more. Only on a massively long form  through the transport agency which makes it pretty much impossible as it ask a lot of stupid questions such as do you have permission from the owner to get this information yes / no, if yes please attach a file proving written confirmation from the owner. Even then it seems to be at the nzta discretion whether they give you the information or not. 

Someone owes me money. I know two possible number plates to search.